add results on TridentNet's readme
add results on TridentNet's readme

Reviewed By: wanyenlo

Differential Revision: D17858209

fbshipit-source-id: 8f6b306b58970af1a461cba7d38c95e339a7acfa

facebookresearch/detectron2,facebookresearch/detectron2,facebookresearch/detectron2